Semiconductor lasers, which are optical semiconductor devices, have been widely used in various wavelength ranges. Among those semiconductor lasers, Distributed Feed-Back (DFB) lasers and Distributed Bragg Reflector (DBR) lasers have been used in communication applications and also used as a light source of an imaging device requiring a monochromatic laser. This is because those DFB and DBR lasers may lase in a single longitudinal mode.
Moreover, reliability and service lifetime of a semiconductor laser are main factors to be considered when the semiconductor laser is put into practical use. In this regard, optical damage (which may be called Catastrophic Optical Damage (COD)) to an end surface of the semiconductor device may often become a major determinant factor for the service lifetime of the semiconductor lasers.
Further, in a case where the maximum output and the like of the semiconductor laser is likely to be limited due to the COD thereof, if it is desired for the semiconductor device to output high power, it may be desired that the COD is controlled (reduced).
Reference may be made to Japanese Laid-open Patent Publication Nos. 2001-230491, 2001-94207, and H09-23037.